Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus including the electrophotographic photosensitive member.
Description of the Related Art
Currently, an electrophotographic photosensitive member is generally a functional separation type laminated photosensitive member in which a charge-generating function (charge generating layer) and a charge-transporting function (charge transporting layer) are shared in respective separate layers.
With respect to a charge-generating substance having the charge-generating function, the emission wavelength of a semiconductor laser commonly used as an image exposing unit is as long as from 650 to 820 nm, and therefore a charge-generating substance having a high sensitivity to light of a long wavelength is developed in progress.
A phthalocyanine pigment is effective as such a charge-generating substance having a high sensitivity to light up to a long wavelength region, and in particular, oxytitanium phthalocyanine and gallium phthalocyanine, having excellent sensitive characteristics, have been heretofore reported with respect to various crystal forms and improved production methods.
Japanese Patent Application Laid-Open No. H07-331107 discloses a hydroxygallium phthalocyanine crystal containing a polar organic solvent. N,N-dimethylformamide is used for a conversion solvent to thereby allow the polar organic solvent to be incorporated in the crystal, providing a crystal having excellent sensitive characteristics.
On the other hand, the charge transporting layer sharing the charge transporting function is demanded to have mechanical strength and less degradation of discharge because of having the charge transporting function and being located on the outermost surface of the electrophotographic photosensitive member. Accordingly, a charge transporting material having high mobility and a resin having a strong mechanical strength and having resistance to discharge are developed in progress.
In particular, a problem is that the charge transporting layer is made thinner due to abrading in repeated use of the photosensitive member, to thereby result in an increase in electric field strength to cause fogging (a phenomenon where a toner is slightly developed in a region in which the toner is not to be essentially developed).
Japanese Patent Application Laid-Open No. 2011-026574 describes a polycarbonate copolymer excellent in wear resistance, and provides a photosensitive member excellent in wear resistance.